Fluid flow induced cavity resonance is a source of unwanted noise and vibration which occurs during travel of vehicles such as marine vessels, automobiles and aircraft as well as during flow of fluid through certain pipe systems. Such acoustic problem arises when fluid within an opening in a structural portion of the vehicle through which an enclosed cavity is exposed to the fluid, becomes unstable so as to excite cavity resonance. Various methods have been utilized and/or proposed in order to reduce or eliminate the cavity resonance condition, including installation of slatted louvers in the opening, use of spoilers or flaps at the leading edge of the opening or use of a ramp shaped trailing edge for the opening. Such structural solutions to the problem have various operational limitations and adverse affects such as blocking the opening and increasing broadband noise. Other solutions to the foregoing acoustical problem involve costly installation of electronic equipment which not only adds to the vehicle weight but does not completely eliminate the acoustic oscillations.
It is therefore an important object of the present invention to more completely eliminate cavity resonance without use of costly electronic equipment heretofore utilized, and without blockage of the opening or causing other unwanted noises.